Unclaimed Pension / United States Rubber Company

I'm in the hunt for an unclaimed pension for my father, who was employed from 1950 to 1961, with the company formerly known as the U.S. Rubber Company. I've checked a number of the usual sources, including the Pension Benefit Guarantee Corporation and a number of what I thought might be the successor companies to the U.S. Rubber Company including: Dunlop, Uniroyal, Firestone, Goodyear, Wingfoot and even Locheed Martin. Contacts with these benefit departments reflect no record of my father's employment, mostly since it does not appear as though any of these companies are the successor plan administrators of my father's pension plan.

I'm pretty sure that my father's pension can't be a whole heck of a lot, but now after 20 years post-retirement, even if his benefit was $50 or $100 per month - that might amount to something, although he's far from destitute and in desparate need of the money. I'm not even sure if he was vested in a pension, or whether a defined benefit pension plan was even offered by his company. I know that current plan rules vest employees after 5 years, and the prior length of time until vesting was 10 years, but back in 1961 (I was seven years old then), I can't even begin to speculate on what the vesting rules were.

Mostly, I'm kind of hoping that a former U.S. Rubber Company employee (or relative), will see this posting and contact me with the name of the current plan administrator (if one exists at all). Alternately, anybody having substantive suggestions beyond what I've already tried and researched (and I've researched a good amount so far), feel free to weigh-in. Thanks!